As a method of forming a solder bump on an electronic component, substrate or the like (hereinafter called a work), a method of using a solder ball is known. This method is to mount a solder ball on an electrode of a work, and heat to fuse the solder ball, thereby bonding the solder to the electrode. At the junction of the solder ball and electrode, in order to improve the bonding performance, a solder paste containing solder particles in the flux is applied. At this time, the methods of application include a method of applying a solder paste to the lower end of the solder ball preliminarily, and a method of transferring the solder paste by using a pin and applying on the electrode surface.
Depending on the type of the electronic component, a solder bump may be formed on a recess provided in an insulating layer covering the electrode such as TAB tape. In such a case, since the solder ball for forming a bump must be bonded with solder so as to be in conductive state with the electrode formed in the bottom of the recess, the solder paste must be applied in the inside of the recess.
However, since the solder paste is an adhesive paste material, it is not easy to fill in the recess uniformly. In particular, in the higher density trend of electronic components, since the aperture of recess is smaller than the diameter of the solder ball or the size of the transfer pin, it is more difficult to fill the recess with solder paste.
Sufficient filling with solder paste may be realized by a method of filling the recess with solder paste by printing by using a stencil mask, but this method requires a solder paste printing device, and the equipment cost is increased and the process is complicated, and it is hence not preferred. If attempted to bond with solder while filling with solder paste is insufficient, bonding with the electrode surface is defective, and a favorable solder bump is not formed.